Thor hainanensis, Xu, Peng & Li, Xinzheng, 2014

Xu, Peng & Li, Xinzheng, 2014, A new species of the hippolytid shrimp genus Thor Kingsley, 1878 (Crustacea: Decapoda: Caridea) from Hainan Island, China, Zootaxa 3795 (3), pp. 394-400 : 394-399

publication ID	https://doi.org/ 10.11646/zootaxa.3795.3.10
publication LSID	lsid:zoobank.org:pub:84469758-B2C9-4357-B048-4029B2494EB9
DOI	https://doi.org/10.5281/zenodo.6138680
persistent identifier	https://treatment.plazi.org/id/03BC8797-FF83-CD67-FF4D-F8FAFD6B1662
treatment provided by	Plazi
scientific name	Thor hainanensis
status	sp. nov.

Treatment

Thor hainanensis sp. nov.

( Figs 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Material examined. Holotype, ovigerous female, MBM136607, cl 1.8mm, intertidal, Sanya, Hainan Island, 5 March, 1997, coll. Xinzheng Li.

Paratypes, 1 male, MBM136405, cl 1.9mm, intertidal, Qionghai, Hainan Island, 4 April, 1992, coll. Xinzheng Li; 5 ovigerous females, MBM136387, cl 1.7–2.1mm, intertidal, Lingao, Hainan Island, 2 December, 1990, coll.

Huilian Chen; 4 ovigerous females, MBM136589, cl 1.8–1.9mm, intertidal, Sanya, Hainan Island, 1 March, 1997, coll. Xinzheng Li; 5 ovigerous females, MBM136394, cl 1.8–2.0mm, 0–2m, Lingshui, Hainan Island, 26 March, 1992, coll. Xinzheng Li.

Diagnosis. Rostrum with bifid appearance about half length of carapace; carapace with developed antennal tooth and minute pterygostomian tooth; third segment of antennular peduncle with subtriangular dorsal scale. Abdomen rounded dorsally; pleurae of fourth and fifth abdominal somites each with small posteroventral tooth; dorsal surface of telson with 3–5 pairs of dorsolateral spines. Mandible only with incisor process and molar process. Third maxilliped with exopod and epipod. First pereopod with epipod; carpus on the second pereopod with six-segmented. Third and fourth pereopods prehensile, subchelate in male; second pleopod with appendix masculine about 0.9 length of appendix interna.

Description. Holotype female. Small hippolytid shrimp without supraorbital spine.

Rostrum ( Fig. 1 View FIGURE 1 A, B) about half length of carapace, nearly straight, slightly descending, reaching but not exceeding basal segment of antennular peduncle; dorsal margin with three teeth, posterior one on carapace posterior to margin of orbit; ventral margin armed with only one subterminal tooth, giving rostrum bifid appearance; lateral carina feebly developed.

Carapace ( Fig. 1 View FIGURE 1 A) with inferior orbital angle slightly produced, subacute; antennal tooth moderately developed; pterygostomian tooth minute; anterolateral margin between antennal tooth and pterygostomian tooth obscurely angulate.

Abdomen ( Fig. 1 View FIGURE 1 A) rounded dorsally. Pleurae of fourth and fifth abdominal somites each with small posteroventral tooth. Sixth somite 1.9 times as long as fifth mid-dorsal length. Telson ( Figs 1 View FIGURE 1 A, 2B) about 1.2 times longer than sixth abdominal somite; dorsal surface with three pairs of dorsolateral spines and three pairs of terminal spines, lateral pair similar to dorsolateral series.

Eye ( Fig. 1 View FIGURE 1 A) subpyriform, pigmented; cornea with distinct ocellar spot, shorter than stalk.

Antennular peduncle ( Figs 1 View FIGURE 1 A, 2A) reaching distal 0.4 of antennal scale. Basal segment with strong subdistal, ventromesial tooth; sharp stylocerite reaching slightly beyond distal margin of second segment, armed with little indistinct tooth near proximal end of lateral margin; second segment with curved lateral spine reaching beyond mid-length of distal segment; third segment with subtriangular dorsal scale. Outer flagellum stout and heavily setose. Inner flagellum slender, elongate, with 23–28 segments.

Antennal peduncle ( Fig. 1 View FIGURE 1 A) with basicerite bearing strong distal, ventrolateral tooth, dorsodistal angle bluntly produced. Carpocerite overreaching second segment of antennular peduncle. Antennal scale shorter than length of carapace, 2.4 times as long as wide; lateral margin faintly concave, with distolateral tooth exceeded by lamina.

Mouthparts ( Fig. 2 View FIGURE 2 C–G) typical of genus. Mandible without palp; incisor process slender, with series of four subequal, tiny, distal teeth; molar process stout.

Third maxilliped ( Fig. 2 View FIGURE 2 H) long and slender, somewhat beyond antennal scale; ultimate segment 4.3 times longer than penultimate segment, with corneous spines distally; antepenultimate segment subequal in length to ultimate segment, distoventral margin with small spine. Exopod exceeding middle of antepenultimate segment; epipod present.

First pereopod ( Figs 1 View FIGURE 1 A, 2I) with strap-like, terminally hooked epipod; moderately stout, falling short of distal margin of antennal scale. Chela about 1.2 times longer than carpus, 3.1 times longer than wide; dactylus with bifid tip, slightly longer than half length of palm; palm subcylindrical, 2.1 times as long as wide, fixed finger terminating in single corneous claw. Carpus 3.1 times longer than wide. Merus subequal in length to carpus, 2.3 times as long as wide.

Second pereopod ( Fig. 2 View FIGURE 2 J) slender and chelate; carpus with six sub-segments, third sub-segment longest. Merus shorter than carpus, 6.3 times longer than width. No epipod.

Third pereopod ( Fig. 2 View FIGURE 2 K) overreaching antennal scale by the length of dactylus; biunguiculate dactylus 0.2 times as long as propodus, about 2.6 times longer than high, armed with three accessory spines along entire length of flexor margin; propodus 10 times as long as wide; flexor margin with about 9–10 spinules, spinules increasing in size distally; carpus less than half length of propodus, 2.9–4.2 times longer than wide. Merus about equal to propodus, 5.9 times longer than deep, with prominent lateral spines distally. Ischium unarmed.

Fourth pereopod ( Fig. 2 View FIGURE 2 L) similar to third pereopod, overreaching antennal scale, biunguiculate dactylus armed with four accessory spines along entire length of flexor margin; merus with one distolateral spine. Fifth pereopod ( Fig. 2 View FIGURE 2 M) with no meral spine.

Pleopods ( Fig. 1 View FIGURE 1 A) without special features. Uropods ( Fig. 2 View FIGURE 2 B) longer than telson, fringed with setae; outer branch of uropod with fixed tooth and movable spine along suture.

Paratype females. Very similar to holotype female except for following: merus of third pereopod armed with two distolateral spines; merus of fifth pereopod with one distolateral spine; dorsal surface of telson with four or five pairs of dorsolateral spines.

Paratype male. Third pereopod ( Fig. 3 View FIGURE 3 A) prehensile, subchelate. Dactylus ( Fig. 4 View FIGURE 4 B) with bifid tip and many closely appressed spinules on flexor margin; propodus ( Fig. 4 View FIGURE 4 A, B) more than twice as long as dactylus, distal third of flexor margin with densely spinules; carpus less than half as long as propodus; merus slightly shorter than propodus, armed with strong spine near distal end of lateral surface. Fourth pereopod ( Fig. 3 View FIGURE 3 B) similar to third pereopod, prehensile, subchelate; merus also armed with one distolateral spine. Second pleopod ( Fig. 3 View FIGURE 3 C) with appendix masculine moderately stout, almost 6 times as long as wide, about 0.9 length of appendix interna, bearing about 5 long stiff setae.

Coloration in life. Unknown.

Distribution. Only known from the type locality, Hainan Island. Specimens collected from shallow intertidal coral reef pools at depths of 2– 15m.

Etymology. The name is derived from the type locality, Hainan Island, in the South China Sea.

Remarks. The most important morphological character of the new species is the presence of an epipod ( Fig. 5 View FIGURE 5 A, B) on the first pereopod. The fourth pereopod ( Fig. 4 View FIGURE 4 C, D) of male specimen is prehensile and subchelate, also rare and unique in the genus.

Besides the epipod on the first pereopod, the new species can be easily distinguished from the known species in the genus.

The new species is very similar to Thor cocoensis Wicksten & Vargas, 2001 . It can be distinguished from the latter by (1) the dorsal margin of rostrum armed with three teeth in T. hainanensis , however, T. cocoensis bearing only one or two dorsal teeth; (2) the tip of rostrum shows distinctly bifid in T. hainanensis , vs. the tip of rostrum is acute in T. cocoensis •

The new species distinguishes from Thor cordelli Wicksten, 1996 , T. dobkini Chace, 1972 , T. floridanus Kingsley, 1878 , T. manningi Chace, 1972 , T. spinipes Bruce, 1983 and T. spinosus Boone, 1935 by the entirely lacking of a distinct supraorbital spine or its vestige.

The telson of Thor intermedius Holthuis, 1947 has only one pair of very minute spinules on the posterior half of the dorsal surface; the stylocerite of T. paschalis ( Heller, 1862) totally lacks the little tooth at basal part of ourter margin ( Holthuis, 1947). These morphological differences make a distinction from T. hainanensis .

The new species can be distinguished from Thor marguitae Bruce, 1978 by the rostrum with bifid tip. In ovigerous females, T. marguitae has a more strongly developed rostrum, with typically a trifid tip.

Thor amboinensis (de Man, 1888) is well-known by associated with all kinds of coelenterates and always has a distally acute simple rostrum, without any evidence of ventral teeth. Apart from the existence of epipod on the first pereopod, T. hainanensis can be easily distinguished from T. amboinensis by its smaller body and bifid tip rostrum ( Holthuis, 1947; Miyake & Hayashi, 1966).